China is routinely ranked as one of the most repressive nations in terms of press freedoms and free speech, but thanks to a social media site, more Chinese are speaking more freely than ever before. Weibo is China's answer to Twitter. Just four years old, it has hundreds of millions of users and increasingly Chinese are using it to expose corruption and criticize officials.

NPR's Frank Langfitt reports on the Weibo revolution and how China's Communist Party is trying to control it.

FRANK LANGFITT, BYLINE: Were it not for Weibo, you would never know Tang Hui's extraordinary story. She wouldn't be here to tell it. She'd be sitting in a Chinese re-education through labor camp eating porridge. Instead, Tang's back home at her dining room table in Hunan Province sharing her Kafka-esque tale. It began six years ago, when a pimp lured her then-11-year-old daughter into a brothel in the central Chinese city of Yongzhou.

TANG HUI: (Through translator) He said if you cry, I am going to go kill your mom. I know where your mother's business is and I know your mother.

LANGFITT: The fifth grader was forced to service scores of clients. After three months, Tang got a tip about her daughter's location and called the cops. But Tang says the first officer to arrive at the brothel never got out of his car. And even after she convinced police to rescue her daughter, they wouldn't arrest anyone.

HUI: (Through translator) We demanded that they take notes when interviewing my child. They repeatedly refused. They said this was not a criminal case.

LANGFITT: Later, Tang found out why the police were so reluctant. The brothel owner had an uncle who was a top official in the local prosecutor's office. A court did eventually convict the brothel staff. But Tang continued to demand punishment for the police who tried to shield them. In August the police had had enough and called Tang in.

HUI: (Through translator) When I arrived at the police station, I saw they had seven to eight special forces police there to guard me. They asked me to sit in a chair for interrogation. I spent a night in the chair and didn't sleep at all. The next morning, at 7:30, they gave me a paper saying I was going to re-education through labor camp.

LANGFITT: For 18 months - so lawyer, no trial. Seemingly no hope. But before the cops hauled her off, Tang called her attorney. He posted the news to his Weibo account. Within days, Tang's story had reached more than 30 million Weibo users, and they were furious. A torrent of criticism followed, overwhelming the local police.

UNIDENTIFIED MAN: (Speaking foreign language)

LANGFITT: After 10 days, state-run China Central Television announced Tang's release. Tang says a few years ago this couldn't have happened.

HUI: (Through translator) Weibo had a very big impact on my situation because our local government tried to cover up this case and not let the public know. But this time people around China and even around the world found out they put me in labor camp. And the local government couldn't resist so many people's power.

MICHAEL ANTI: Chinese Weibo basically is first ever in the Chinese history the public sphere.

HU YONG: Any local news can immediately become national news.

ISAAC MAO: Weibo is the battleground between the authority and freedom-thinking people.

LANGFITT: That's political commentator Michael Anti, Peking University Professor Hu Yong and Isaac Mao, one of China's first bloggers. Weibo is changing the way Chinese communicate and has become a major source of news here. Hu Yong says Weibo has also become a powerful new tool for ordinary people to protect their rights.

YONG: Before the emergence of Weibo, local people actually they have very limited channels to try to solve their problems. But Weibo is - kind of pressure politics on local government officials.

LANGFITT: In recent months Weibo campaigns have triggered a number of firings. They include officials in western China who forced a woman to abort her seven-month-old fetus, and a safety chief who was photographed wearing various luxury watches as well as smiling at the scene a fatal bus accident. Observers call it Weibo justice.

Why does China's famously thin-skinned regime put up with such criticism? Michael Anti says when it's directed at local officials, those attacks actually serve the central government.

ANTI: Chinese have a long time myth that the emperor is good, all the thugs are local. So that myth is very important to keep the regime their legitimacy. So I think Weibo justice is exactly a showcase for the central government to tell the people that, you know, the emperor is still good.

LANGFITT: On occasion the party will even allow netizens, or Wangmin, as they're known in Chinese, to attack high-ranking officials it wants to get rid of. That's what happened to then-Chongqing Party boss Bo Xilai, who was lobbying for a top post in Beijing and had lots of political enemies. After Bo's police chief hid out in a U.S. consulate this year, Anti says it was open season on Weibo.

ANTI: Two months, you can joke about Bo Xilai and Chongqing City, about everything. Weibo became a very convenient platform.

LANGFITT: The party though won't tolerate anything it remotely sees as a threat. Authorities detained a Beijing blogger earlier this month after he jokingly imagined the recent party leadership congress as a horror movie in which the delegates die en masse. Of course like most Americans, most Chinese don't use Weibo for politics. They use it to pursue their interests, and sometimes to help strangers who share them.

RICHARD SEARS: My name is Richard Sears and for the past 22 years now I've been working on a website of the etymology of Chinese characters.

LANGFITT: Sears is a retired computer programmer from Tennessee. He came to China this year to do research for his website, a personal hobby. But he says because of bad information his tourist visa was cancelled in August.

SEARS: They confiscated my passport. I found myself with 10 days to get out of the country. At that point I figured I would have to go home and never come back to China.

LANGFITT: Sears had one thing going for him.

SEARS: I had a few friends on Weibo. I didn't realize how many friends I had on Weibo, but I told a couple of my friends about it and then suddenly, within a couple of days, there were 40,000 re-tweets.

LANGFITT: Job possibilities poured in from Chinese supporters trying to help Sears stay in the country. Last week Sears arrived back in Beijing with a work visa and a job teaching physics and doing Chinese language research at Beijing Normal University.

SEARS: Without Weibo, this would have been impossible.

LANGFITT: Weibo is still in its infancy. China's government and the microblog companies themselves employ an army of censors every day to manage and shape its growth. Sears isn't sure how Weibo will ultimately evolve. But he thinks the potential is huge. Frank Langfitt, NPR News, Shanghai.

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